In recent years, electronic devices provided with a touch panel are being widely used as a component to detect user operation in mobile terminals such as smartphones, information devices such as tablet PCs, calculators, or ticket vending machines, household appliances such as microwave ovens, televisions, or lighting appliances, industrial devices (factory automation equipment), and the like.
An electronic device provided with a touch panel typically displays the image of an operation key or button, an icon, or the like (referred to below as an “object”) on the display screen of a display unit such as a liquid crystal display disposed on the back face of the touch panel. In such an electronic device, when the user contacts the touch panel at a position corresponding to an object displayed on the display screen, the touch panel detects contact at that position. Hence, in such an electronic device, a user interface with a high degree of freedom can be implemented in accordance with a variety of application software.
Many types of such a touch panel are known, including a resistive film type, a capacitive type, and an optical type. All of these types of touch panels, however, simply detect an operation by the user's finger, a stylus pen, or the like. Upon being contacted, the touch panel itself is not physically displaced like a mechanical push-button switch. Accordingly, even if the user performs an operation on the touch panel, the user cannot receive any feedback for the operation.
To address this issue, a feedback method for generating vibration upon detection of an operation on the touch panel has been proposed (for example, see Patent Literature 1). Patent Literature 1 discloses an example of using a piezoelectric element as a vibration unit. By causing a piezoelectric element to expand and contract, this vibration unit can cause the touch panel to flex, generating vibration. In this way, the input device in Patent Literature 1 can provide a tactile sensation to the user when the user operates the touch panel. In other words, a recent electronic device such as a mobile phone provided with a touch panel, as disclosed in Patent Literature 1, has a function (referred to below as a “tactile sensation providing function”) to provide a tactile sensation to the user by vibrating a vibration unit, such as a vibrator or piezoelectric element included in the electronic device, when the user touches the touch panel, thereby notifying the user that the user operation was input into the electronic device. As well as providing the tactile sensation, by executing predetermined processing based on the operation, the electronic device can notify the user that the operation has been appropriately recognized.